Was it poisoning?

Abstract

The aim of post-mortem toxicology is to help establish the role that drugs or other poisons played in a death, or in events immediately before death. If self-poisoning is suspected then the diagnosis may be straightforward and all that may be required is confirmation of the agents involved. If the cause of death is not immediately obvious, however, then suspicion of possible poisoning is of course crucial. Blood sampling (needle aspiration, peripheral vein, e.g. femoral, ideally after proximal ligation) before opening the body, minimises the risk of sample contamination with, for example, gut contents or urine. The site of blood sampling should always be recorded. Other specimens (stomach contents, urine, liver, vitreous humor) may also be valuable and may be needed to corroborate unexpected or unusual findings in the absence of other evidence. The availability of ante-mortem specimens should not preclude post-mortem sampling. Appropriate sample preservation, transport, and storage are mandatory. Interpretation of post-mortem toxicology must take into account what is known of the clinical pharmacology, including pharmacokinetics, and toxicology of the agent(s) in question, the circumstances under which death occurred including the possible mechanism(s) of exposure, and other factors such as the sample(s) analysed and the analytical methods used. It was thought that concentrations of poisons measured in blood obtained at autopsy reflected the situation peri-mortem. However, we now know that changes may occur in the composition of body fluids, even peripheral blood, after death. Such changes are likely to be greater with centrally-acting drugs such as clozapine with large volumes of distribution, and may perhaps be minimised by prompt refrigeration of the body and performing the autopsy quickly. Better training in analytical toxicology is needed for pathologists and others who may be called upon to interpret toxicological data for the Courts. Undue reliance on quantitative results is likely to confuse sooner rather than later, especially in the case of centrally-acting drugs such as opioids and clozapine. Remember that the question is normally "was it poisoning?" or "was it an overdose?"--and not--"is it a fatal level"?